Method of treating iron or steel articles.



OF BQSTGN,

llfD tTAT FATE-El i tll l ilfifii MASSACHUSETTS.

METHGZD 03F TREATING IREN STEEL ARTICLES.

Flo Drawing.

To all whom "it may concern:

Be it known that l, Haney HOWARD, i citizen of the Uniteti States, resitlin at Boston, in the county of Sutlollt antl btate of Massachusetts,have invented certain new and useful Improvements in Methods of Treating Iron '01 Steel Articles. of which the following: is a specification.

This invention relates to the preparation of sheets or other forms of iron and steel for tinning or galvanizing.

it is well known that tinned plates are very frequently imperfect by reason of the presence of minute uncot'eretl areas, pea-fora tions, or so-calletl "pin holes inthe coatng metal,

such imperftarlions beingfhi ghly detrimental by reason of the tendency of the coated metal to become eorrotletl or pitted at these points or areas. While all surfaces otiron or steel which have been thoroughly cleaned and freed from grease or oxid are very susceptible to oxidation or LQIlQSlOIl, suci imperfections are particularly liable to occur in plates which have been SllllJQClttl to an acid pickljngprocess; and their pres ence may in this case be partly or wholly attributed to the persistence in the metal to be coated of acid conditions arising from the baths employed for the removal of the scale.

The object of the present invention is the provision of a more rapid and etl'ective method of securing complete anti certain elimination of such acid conditions, and in general a more complete pietection of coated surfaces from corrosive influences, than is racticable'by known methods, in the case of with alkaline so utions.

According to the preferred embodiment of the invention, the iron or steelarticles are first freed from scale by the usual methods, as"by, immersion acid pickling bath. The articles are then immersed, preferably after a brief Washing or rinsing with water or a suitable alkaline solution, in an alkaline electrolyte, being connectetl therein as the cathode. As electroiytes, solutions containing a carbonate or for example ickled plates, by washing Specification of Letters Patent.

for a suitable time in an hytlrortizl of an alkali are Patented iteh. l5,

Application filed November 16, will). Serial lilo. 528,389.

lilOS'i Stumble. i'ln electric current nissetl to the sheet or other article as cathode, resulting in the deposition or separation of the alkali metal, and by secondary reaction of-this metal with the water of the SOl'tlllOll, in an evolution of hydrogen at the surface of the metal. By this procedure the cleaned surfaces are rentleretl far less liable to cmrrosion, any residual aeitl conditions are quickly eliminated, and the metal may inunetliately receive a coating of tin or zinc by ininiersion in the molten? metal in the usual waf l am aware that it has been proposetl'to clean metal sheets, preliniiiairy to coating theni, by eouneetii'igthenras cathode in acid or alkaline solutions, but in such cases the purpose has been to atilize the evolved gas for the mechanical removal of scale, grease anti the like. that is to say for cleaning the. plates; whereas according, to the present inrention the electrolytic treatment is a 'iplietl to sheets or articles which have already undergone a cleaning operation, and which by reason of their -freeclom from scale or grease are highly susceptible to corrosion, the purpose of the treatment being to render the plates e articles less liable to subsequent pitting or corrosion and to secure in a rapid anal certain manner the elimination of all residual acid conditions and the provision oi" a surface which is capable of receiving, by the usual coating methods, a moreperlm". film of coating metal.

l claim The, method oi preparing iron and. steel articles for tinnine: or galvanizing, which consists in subjecting the articles to an acid pickling proc 5%; to remove the scale and thereafter pas. mg an electric current to the cleaned articles connected as catholic in an alkaline electrolyte. 

